Adaptive radiotherapy in locally advanced esophageal cancer with atelectasis: a case report

A 65-year-old male patient with a 3-month history of dysphagia was diagnosed with locally advanced thoracic esophageal squamous cell cancer, cT4bN1M0, stage IVA (Union for International Cancer Control TNM 8th edition) (Fig. 1a and b). The primary esophageal tumor components, including primary esophageal cancer and nearby metastatic lymph nodes, were bulky. The lumen of the left bronchus was almost completely obstructed by compression of the tumor masses (Fig. 1c and d). The patient was referred to our specialized hospital for treating the thoracic esophageal cancer. On the day of admission, he presented with dyspnea and decreased arterial oxygen saturation (approximately 90% under room air conditions). As opposed to the findings of chest radiography performed 26 days before admission (Fig. 2a), a mediastinal shift with left atelectasis was detected on chest radiography performed on the day of admission (Fig. 2b). Contrast-enhanced computed tomography (CT) revealed that the mediastinal shift was due to complete obstruction of the left bronchus by the primary esophageal tumor components. The patient had a good overall performance status and good organ function immediately before the left bronchial obstruction; therefore, he was recommended to undergo definitive chemoradiotherapy with curative intent rather than palliative bronchial stent placement, and the patient consented to this treatment. Chemoradiotherapy was initiated on the following day and it comprised three-dimensional conformal radiotherapy with 60 Gy in 30 fractions with concurrent administration of cisplatin (70 mg/m² on day 1 and 29) and 5-fluorouracil (700 mg/m² on days 1–4 and 29–32). Radiotherapy comprised four coplanar irradiation fields, including the gross tumor volumes with adequate margin and elective nodal irradiation for paraesophageal and paratracheal lymph nodes (Fig. 3a–c). Tumor location was monitored with cone-beam CT and chest radiography during the course of chemoradiotherapy. On chemoradiotherapy day 8, follow-up chest radiography revealed no evidence of the mediastinal shift (Fig. 2c). CT simulation was reperformed for adaptive radiotherapy accounting for the geometrical changes resulting from the absence of the mediastinal shift during the course of chemoradiotherapy. In this manner, the adaptive radiotherapy plan ensured correct dose delivery to the primary esophageal tumor components (Fig. 3d–f). Adaptive radiotherapy improved the target coverage, such that the doses covering 98% of the planed target volume (D98%), D50%, and D2% were 92, 100, and 105%, respectively, of the prescribed dose in the adaptive radiotherapy plan compared with 7, 97, and 106%, respectively, of the prescribed dose in the non-adaptive radiotherapy plan. After a dose delivery of 40 Gy, the irradiation fields were additionally cone downed to irradiate the gross tumors alone. After completion of the radiotherapy and concurrent chemotherapy plan, two courses of adjuvant chemotherapy were administered every 4 weeks: cisplatin (80 mg/m² on day 1) and 5-fluorouracil (800 mg/m² on days 1–5). The patient completed the planned treatment course with chemoradiotherapy and adjuvant chemotherapy with no grade ≥ 3 non-hematological adverse events. Complete response was confirmed by esophagogastroduodenoscopy and CT performed at 7 months after initiating chemoradiotherapy (Fig. 4a and b). At present, the patient has shown no disease recurrence, dysphagia, or respiratory symptoms at 13 months after initiating chemoradiotherapy. No radiotherapy-related adverse events were observed, except for radiation-induced grade 2 hypothyroidism.